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小秦岭地区的东闯金矿是中国的超大型金矿床之一,被认为是典型的造山带型金矿床,但其成矿时间有争议。矿床地质特征研究表明,成矿作用可分为粗粒黄铁矿—石英、细粒黄铁矿—石英、多金属硫化物、碳酸盐—石英四个阶段。笔者分别于两个实验室测定了第Ⅰ、Ⅲ和Ⅱ阶段的氩氩年龄,测定结果表明,Ⅰ阶段石英氩氩坪年龄为142.9±2.9Ma;Ⅱ阶段绢云母氩氩坪年龄为132.2±2.6Ma,等时线年龄为132.6±2.7Ma;Ⅲ阶段石英氩氩坪年龄为128.3±6.2Ma,与地质实际吻合并可相互印证。本文结果表明成矿作用发生在143～128 Ma,侏罗纪—白垩纪之交的挤压—伸展转变期,显示挤压伸展转变期的减压增温环境是造山带型矿床最为有利的成矿地球动力学背景。
The Dongchuang gold deposit in the Xiaoqinling Mountains is one of the super-large gold deposits in China and is considered as a typical orogenic belt type gold deposit. However, the timing of metallogenesis is controversial. The study of the geological characteristics of the deposit shows that the mineralization can be divided into four stages: coarse-grained pyrite-quartz, fine-grained pyrite-quartz, polymetallic sulphides and carbonate-quartz. The authors determined the Argon-Argon ages of stages I, III and II in two laboratories, respectively. The results show that the Argon Argon age at stage I was 142.9 ± 2.9Ma, that of stage II was 132.2 ± 2.6 Ma, the isochron age is 132.6 ± 2.7Ma; the stage Ⅲ quartz argon Argon age is 128.3 ± 6.2Ma, which is consistent with the actual geological conditions and can confirm each other. The results show that the mineralization took place during the transitional period from 143 to 128 Ma at the turn of the Jurassic-Cretaceous period, indicating that the depressurization and warming environment during the crustal transition is the most favorable orogenic belt Mine geodynamics background.